Mass spectrometric studies of cis- and trans-1a,3-disubstituted-1, 1-dichloro-4-formyl-1a ,2,3,4-tetrahydro-1H-azirino [ 1,2-a] [1,5] benzodiazepines

The mass spectrometric behaviour of four cis- and trans-la, 3-disubstituted -1,1 -dichloro-4-formyl-1a,2,3,4-tetrahydro-1H-azirino[1, 2-a] [1,5] benzodiazepines has been studied with the aid of mass-analysed ion kinetic energy spectrometry and exact mass measurements under electron impact ioniza-tion. All compounds show a tendency to eliminate a chlorine atom from the aziridine ring, and then eliminate a neutral propene or styrene from the diazepine ring to yield azirino[ 1, 2-6][1,3]benzimidazole ions. These azmno[1,2-a] [1,5]-benzodiazepines can also eliminate HCl, or Cl plus HG simultaneously to undergo a ring enlargement rearrangement to yield 1,6-benzodiazocine ions, which further lose small molecular fragments, propyne or phenylacetylene, with rearrangement to give quinoxaline ions.     

Reaction of 1-amino-, 2-amino-, and 1,2-diaminoimidazoles with β-diketones

1,2-Diamino-4-phenylimidazolium perchlorate condenses with 2 mole of β-diketones to give pyrimido[2′,1′:2,3]imidazo[1,5-b]pyridazinium derivatives, while, like 1-amino-2-mercapto-4-phenylimidazole, to give imidazo[1,5-b]pyridazine derivatives. Salts of 1-benzylideneamino- and 1-(2-thiazolyl)-2-aminoimidazoles react with β-diketones to give substituted imidazo[1,2-a]pyrimidinium derivatives.     

Cyclocondensation of α,Β-unsaturated ketones with 3-amino-1,2,4-triazole

Dihydro-1,2,4-triazolo[1,5-a]pyrimidine derivatives were obtained by condensation of 3-amino-1,2,4-triazole with 1,3-diaryl-1-propen-3-ones. The structure of 5-phenyl-7-(4-methylphenyl)-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine was established by x-ray diffraction analysis.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 229–233, February, 1988.     

Chemistry of acyl(imidoyl)ketenes. 8*. Thermolysis of 3-alkoxycarbonyl- 5-phenyl-1,2,4,5-tetrahydropyrrolo[1,2-a]- quinoxaline-1,2,4-triones. Structure of 2-(3-oxo-4-phenyl-3,4-dihydro-2-quinoxalinyl)- 2,4-di(ethoxycarbonyl)-6-phenyl-2,3,5,6-tetrahydro- 1h-pyrido[1,2-a]quinoxaline-1,3,5-trione

3-Alkoxycarbonylmethylene-1-phenyl-1,2,3,4-tetrahydro-2-quinoxalones, obtained by the interaction of dialkyl esters of oxaloacetic acid and N-phenyl-o-phenylenediamine, react with oxalyl chloride with the formation of 3-alkoxycarbonyl-5-phenyl-1,2,4,5-tetrahydropyrrolo[1,2-a]quinoxaline-1,2,4-triones. Alkoxycarbonyl(2-oxo-1-phenyl-1,2-dihydro-3-quinoxalinyl)ketenes, generated on thermal decarbonylation of the latter, are stabilized by participation in a [4+2] cyclodimerization reaction with the formation of 2,4-di(alkoxycarbonyl)-2-(3-oxo-4-phenyl-3,4-dihydro-2-quinoxalinyl)-6-phenyl-2,3,5,6-tetrahydro-1H-pyrido[1,2-a]quinoxaline-1,3,5-triones. The crystal and molecular structure of the di(ethoxycarbonyl) derivative have been investigated by X-ray structural analysis.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1501–1506, October, 2004.     

Ring contraction of thia(seleno)diazine rings into pyrazoles in the reaction of 3-aryl-10-methyl-2H-1,3,4-thia(seleno)diazino[3, 2-a]benzimidazolium salts with bases

Reaction of 3-aryl-10-methyl-2H-1,3,4-thiadiazino[3,2-a]benzimidazolium salts with triethylamine led to ring contraction of the thiadiazine ring to a pyrazole ring with the formation of a mixture of derivatives of 3-mercaptopyrazolobenzimidazole and di(pyrazolo[1,5-a]benzimidazolyl-3) disulfide. The disulfides were formed exclusively when these salts react with ethanolic alkali. The reaction with potassium carbonate in acetic anhydridegave3-acetylthiopyrazolo[1,5- a]benzimidazoles. 2-Aryl-4- alkylpyrazolo[1, 5- a]benzimidazoles were formed by heating thiadiazino[3,2-a]benzimidazolium salts in formamide and by treating selenodiazino[3,2-a]benzimidazolium salts with potassium carbonate in acetic anhydride.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1698–1705, 1992.     

Pyrimidine acyclo-C-nucleosides by ring transformations of 2-formyl-L-arabinal

The protected 2-formyl-L-arabinal 2 reacted with thiourea and cyanamide in the presence of sodium hydride to afford via ring transformations the 5-[1R,2S-1,2- bis(benzyloxy)-3-hydroxypropyl]-1,2-dihydropyrimidines 3 and 4, respectively. Similarly, treatment of 2 with 3-amino-2H-1,2,4-triazole yielded 6-[1R,2S-1,2- bis(benzyloxy)-3-hydroxypropyl][1,2,4]-triazolo[1,5-a]pyrimidine (5).     

The surprising nucleophilic addition of aminochlorocarbenes to diethyl acetylenedicarboxylate and to oxalyl chloride: quinolines and benzo[1,4]diazepines from N-alkylformanilides and oxalyl chloride in the presence of Hünig's base

Vilsmeier reagents derived from N-methylformanilides undergo ready deprotonation with Hünig's base. In xylene, the derived nucleophilic arylaminochlorocarbenes bearing 4-methyl- and 4-methoxy-substituents react with acetylenedicarboxylates to give 2-(2-chloro-1,2-bis(ethoxycarbonyl)vinyl)-3,4-bis(ethoxycarbonyl)-1-methyl-1,2-dihydroquinolines while most derivatives react with oxalyl chloride to give substituted 1-methyl-4 phenylbenzo[f][1,4]diazepine-2,3-dicarboxylic anhydrides.     

Pyrimidine Derivatives and Related Compounds II: Synthesis of some derivatives of pyrimido[1,2:2′,3′]pyrazolo[1,5-a]pyrimidines,a new ring system

3,5-Diamino-4-phenylazo-pyrazoles ( 1a–1c ) react with acetylacetone and with ethyl acetoacetate to yield the corresponding pyrazolo[1,5-a]pyrimidine derivatives 2a–2c and 3a–3c , respectively. Whereas 1a–1c add readily to methyl acrylate yielding the 4,5,6,7-tetrahydropyrazolo[1,5-a]-pyrimidine derivatives 5a–5c, 1a–1c add to methylacrylonitrile or methyl methacrylate only under drastic conditions to yield 5d–5f . The pyrimido[1,2:2′,3′]pyrazolo[1,5-a]pyrimidine derivatives 10a–10c are prepared by the action of acrylonitrile on 2a–2c . Compounds 10a–10c are readily converted into the corresponding oxo derivatives 12a–12c on treatment with acetic acid-hydrochloric acid mixture.     

The reaction of β-lactam carbenes with 3,6-dipyridyltetrazines: switch of reaction pathways by 2-pyridyl and 4-pyridyl substituents of tetrazines

The reactions of β-lactam carbenes with both 3,6-di(2-pyridyl)tetrazine and 3,6-di(4-pyridyl)tetrazine were studied. It was found that β-lactam carbenes reacted with 3,6-di(2-pyridyl)tetrazine to produce 5-triazolo[1,5-a]pyridylpyrrol-2-ones in good yields, while with 3,6-di(4-pyridyl)tetrazine, they afforded pyrido[c]cyclopenta[b]pyrrol-2-ones in moderate yields. Both reactions were proposed to follow cascade mechanisms containing a 3,6a-dipyridylpyrrolo[3,2-c]pyrazol-5-one intermediate. The different pathways of the transformation of pyrrolo[3,2-c]pyrazol-5-ones were switched by the 2- and 4-pyridyl substituents. This work not only provided a simple and efficient strategy for the construction of novel triazolo[1,5-a]pyridine and pyrido[c]cyclopenta[b]pyrrole derivatives, respectively, but also revealed two different thermal transformation patterns of 3H-pyrazole compounds.     

Cyclization of 3-Ethoxycarbonylmethyl-, 3-Cyanomethyl-, and 3-Acetylmethyl-1-amino-2-methylbenzimidazolium Salts Effected by Acetic Anhydride in the Presence of a Base

3-Ethoxycarbonylmethyl- and 3-cyanomethyl-1-amino-2-methylbenzimidazolium chlorides cyclized at treatment with acetic anhydride in the presence of potassium carbonate to afford a mixture of derivatives of pyrazolo[1,5-a]benzimidazole and 4-aminopyrrolo[1,2-a]benzimidazole. Therewith in the first case prevails the process of pyrazole ring fusion, and in the latter pyrrole ring is fused. 3-Aroyl(thenoyl)methyl-1-amino-2-methylbenzimidazolium bromides under the same conditions are converted into 1-aroyl(thenoyl)-2-methyl- and 2-4-acetamido-3-acetylpyrrolo[1,2-a]benzimidazoles.     

Thermolysis of 6-Aryl-1,5-diazabicyclo[3.1.0]hexanes in the Presence of N-Arylmaleimides

Heating of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes in the presence of N-arylmaleimides gives rise to 2,9-diarylperhydropyrazolo[1,2-a]pyrrolo[3,4-c]pyrazole-1,3-diones. It is presumed that thermal cleavage of the C-N bond in the diaziridine fragment of the 6-aryl-1,5-diazabicyclo[3.1.0]hexanes results in formation of labile azomethinimines that react with N-arylmaleimides to afford the products of 1,3-dipolar cycloaddition. The rate of accumulation thereof depends only on the character of substituents in the aromatic ring of the 1,5-diazabicyclo[3.1.0]hexanes and is independent of maleimide. The thermal isomerization of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes without 1,3-dipolarophiles yields the corresponding 2-pyrazolines.     

Cycloaddition of benzoheteroazepine Ⅲ Reaction of 2,3-dihydro-lH-l,5-benzodiazepines with dichlorocarbene and stereo-structures of products

Reaction of 2,3-dihydro-1H-l,5-benzodiazepines with dichlorocarbene generated in situ using benzyltriethylammonium chloride (TEBA) as a phase transfer catalyst in chloroform-aqueous sodium hydroxide mixture gave mainly 1,2-cycloadducts, as and trans-la,3-disubstituted-1, 1-dichloro-1a,2,3,4-tetrahydro-1H-azirino[l,2-a][l,5]benzodiazepines (2,3), and formylated 1,2-cycloadducts, trans-la,3-disubstituted-l, 1-dichloro-4-formyl-1a,2,3,4-tetrahydro-lH-azirino[l,2-a][l,5]benzodiazepines (4). The stereo-structures of cycloadducts and the mechanism are also discussed.     

The reaction of β-lactam carbenes with 3,6-di(2-pyrimidinyl)tetrazine: regulating products by reaction conditions

The reaction of β-lactam carbenes with 3,6-di(2-pyrimidinyl)tetrazine was studied, which produced good yields of novel 5-(3-[1,2,3]triazolo[1,5-a]pyrimidinyl)pyrrol-2-ones or pyrrolo[3′,2′:3,4]pyrrolo[1,2-a]pyrimidin-2-ones under heating at 100 °C or 140 °C, respectively. This work provided a highly efficient strategy for the construction of both [1,2,3]triazolo[1,5-a]pyrimidine and pyrrolo[3′,2′:3,4]pyrrolo[1,2-a]pyrimidine ring systems from the same reactants, and extended the application of β-lactam carbenes in the syntheses of complex heterocycles.     

Reaction of β-lactam carbenes with 2-pyridyl isonitriles: a one-pot synthesis of 2-carbonyl-3-(pyridylamino)imidazo[1,2-a]pyridines useful as fluorescent probes for mercury ion

The one-pot reaction of β-lactam carbenes with 2-pyridyl isonitriles followed by an acidic hydrolysis was reported, which produced 2-carbonyl-3-(pyridylamino)imidazo[1,2-a]pyridines in moderate to good yields. Among the resulting novel imidazo[1,2-a]pyridine derivatives, 1-(6-chloro-3-(5-chloropyridin-2-ylamino)imidazo[1,2-a]pyridin-2-yl)-2-ethylbutan-1-one was demonstrated to be an efficient fluorescent probe for mercury ion both in acetonitrile and in buffered aqueous solution.     

Synthese von imidazo[1,5-a]- und pyrazino[1,2-a]benzimidazolen

1,2-Dihydro-3H-imidazo[1,5-a]benzimidazoles (6), 1-oxo-1,2-dihydro-3H-imidazo[ 1,5-a] benzimidazoles (8), 3H-imidazo[1,5-a]benzimidazoles (7), 3-oxo-1,2,3,4-tetrahydro-pyrazino[1,2-a] benzimidazoles (12), and 3,4-dioxo-1,2,3,4-tetrahydro-pyrazino[1,2-a]benzinudazoles (13) were synthesized from 2-α-aminobenzyl (benzhydryl)-benzimidazoles (2).     

Synthesis of 1,3-diazepines and ring contraction to cyanopyrroles

Several tetrazolo[1,5-a]pyridines/2-azidopyridines undergo photochemical nitrogen elimination and ring expansion to 1,3-diazacyclohepta-1,2,4,6-tetraenes, as well as ring cleavage to cyanovinylketenimines, in low temperature Ar matrices. 6,8-Dichlorotetrazolo[1,5-a]pyridine/2-azido-3,5-dichloropridine undergoes ready exchange of the chlorine in position 8 (3) with ROH/RONa. 8-Chloro-6-trifluoromethyltetrazolo[1,5-a]pyridine undergoes solvolysis of the CF(3) group to afford 8-chloro-6-methoxycarbonyltetrazolo[1,5-a]pyridine. Several tetrazolopyridines/2-azidopyridines afford 1H- or 5H-1,3-diazepines in good yields on photolysis in the presence of alcohols or amines. 5-Chlorotetrazolo[1,5-a]pyridines/2-azido-6-chloropyridines and undergo a rearrangement to 1H- and 3H-3-cyanopyrroles and, respectively. The mechanism of this rearrangement was investigated by (15)N-labelling and takes place via transient 1,3-diazepines. The structures of 6,8-dichloro-tetrazolo[1,5-a]pyridine, 6-chloro-8-ethoxytetrazolo[1,5-a]pyridine, dipyrrolylmethane, and 2-isopropoxy-4-dimethylamino-5H-1,3-diazepine were determined by X-ray crystallography. In the latter case, this represents the first reported X-ray crystal structure of a 5H-1,3-diazepine.     

Novel synthesis of bicycles with fused pyrrole, indole, oxazole, and imidazole rings

Reactions of benzotriazol-1-yl(1H-pyrrol-2-yl)methanone 10 and benzotriazol-1-yl(1H-indol-2-yl)methanone 11 with diverse ketones, isocyanates, and isothiocyanates in the presence of base afforded pyrrolo[1,2-c]oxazol-1-ones 1, oxazolo[3,4-a]indol-1-ones 2, pyrrolo[1,2-c]imidazoles 3, and imidazo[1,5-a]indoles 4 by a simple one-step procedure.     

Formal fusion of a pyrrole ring onto 2-pyridyl and 2-pyrimidyl cations: one-step gas-phase synthesis of indolizine and its derivatives

Two ortho-hetarynium ions, the 2-pyridyl and 2-pyrimidyl cations, react promptly with 1,3-dienes in the gas phase by annulation, formally by fusion, onto the ions of a pyrrole ring. This novel reaction proceeds through an initial polar [4 + 2+] cycloaddition across the C[triple bond]N+ bond, followed by fast ring opening, a [1,4-H] shift, and finally a recyclization that results in a contraction of a six- to a five-membered ring and dissociation by the loss of a methyl radical. For the 2-pyridyl cation, this reaction yields ionized indolizines (pyrrolo[1,2-a]pyridines), while for the 2-pyrimidyl cation, it gives ionized pyrrolo[1,2-a]pyrimidines. The annulation reaction, performed in the rf-only collision quadrupole of a pentaquadrupole (QqQqQ) mass spectrometer, occurs readily with both 1,3-butadiene and isoprene, and is thermodynamically and kinetically favored as predicted by ab initio calculations. Ortho-hetarynium ions and 1,3-dienes provide, therefore, the two building blocks for the efficient one-step gas-phase synthesis of ionized bicyclic pyrrolo[1,2-a]pyridine (indolizine) and pyrrolo[1,2-a]pyrimidine, as well as their analogues and derivatives.     

Cyclocondensation of 5-benzoyl-3-ethoxycarbonyl-6-methylthio-1-R-1,2-dihydropyrid-2-ones with heterocyclic N,N-and N,C-1,3-dinucleophiles

[3+3] Cyclocondensation of 5-benzoyl-3-ethoxycarbonyl-6-methylthio-1-R-1,2-dihydropyrid-2-ones with heterocyclic N,N-and N,C-1,3-dinucleophiles proceeds regioselectively to give a series of new tri-and tetracyclic heterosystems, viz. derivatives of 5,6-dihydropyrazolo[1,5-a]pyrido[2,3-d]pyrimidin-6-one, 1,2-dihydropyrido[2,3-d]pyrido[2′,3′: 3,4]pyrazolo[1,5-a]pyrimidin-2-one, 8,9-dihydro-5H-pyrido-[2,3-d]thiazolo[3,2-a]pyrimidin-8-one, 1,2-dihydrobenzo[4,5]imidazo[1,2-a]pyrido[2,3-d]pyrimidin-2-one, and 1,2-dihydrobenzo[4,5]imidazo[1,2-g][1,6]naphthyridin-2-one.     

Synthesis of 1-functionalized imidazo[1,5-а]pyrazolo[5,1-с]pyrazines

Chemistry of Heterocyclic Compounds - 4-Chloropyrazolo[1,5-a]pyrazines react with ethyl isocyanoacetate to form ethyl imidazo[1,5-a]pyrazolo[5,1-c]pyrazine-1-carboxylates, hydrolysis of which...